Analysis of chicken Wnt-13 expression demonstrates coincidence with cell division in the developing eye and is consistent with a role in induction

We used a degenerate polymerase chain reaction (PCR) strategy to search for Wnt RNA in developing ocular tissues. We isolated a Macaca monkey Wnt-13 P CR fragment, orthologous to the human and murine Wnt-13 and Xenopus Wnt-2b, and a chick Wnt13 cDNA. Wnt-13 is a member of the Wnt-1 class of transform ing Wnt molecules. In situ RNA hybridization revealed a dynamic Wnt-13 expr ession pattern in numerous developing tissues. Within the eye, Wnt-13 is ex pressed in the proliferative epithelium of the lens and both pigmented and nonpigmented layers of the ciliary margin. In vitro BrdU incorporation stud ies coupled with in situ hybridization showed that cWnt-13 expression domai ns in the lens were coincident with cell division. In addition to the eye, cWnt-13 was expressed in head ectoderm, prospective forelimb mesenchyme, lu ng bud, pharyngeal arches, the brain, as well as the otic vesicle. Our data are consistent with previous observations linking transforming Wnts with c ell division and implicate a cascade of events involving cWnt-13 first in d orsoventral patterning and later in cell proliferation regulation associate d with lens development. (C) 1999 Wiley-Liss, Inc.